Measurement of specific IgG antibody levels in serum of patients on regimes comprising high total dose beta-lactam therapy.

Sera from 125 patients receiving mean total doses of beta-lactam therapy of 215 g over a mean of 14 days were assayed by radioimmunoassay. Titres of anti-penicilloyl antibodies, expressed in arbitrary units of specific IgG per microliter of serum (u/microliter), ranged from undetectable (less than 3 u/microliter) to 1,650 u/microliter. There was a higher prevalence of elevated IgG levels in patients who developed haemolytic anaemia or neutropenia compared with patients with no adverse reactions but only in those patients who developed haemolytic anaemia were the antibody titres significantly higher. A subsidiary finding was that a correlation was established between mean total dose and prevalence of positive IgG titres, on a patient group basis (r = 0.87).